I remember an exercise in art school where you had to compile and organize Munsell chips into tint/shade sheets by hue. If you were really ambitious, you could rig up that pages into a cylindrical binding to simulate a 3d color solid.
I loved the progression of digtal color wheels, as you could dynamically play with geometrical harmonies, but always felt a bit offput by the way they handled the introduction of tints, shades. It was tedious to tweak the value of colors manually, and most dynamic transforms seemed to apply globally to the harmony.
This 3D model is much more inuitive to me. And you managed to pack in a powerul set of tranforms in a small, fun UI! I especially like softly pushing the chord around with the global transform joystick!